1. Field of the Invention
The invention disclosed herein relates to enhancement of digital images and, in particular, to techniques for projecting enhanced resolution digital images.
2. Description of the Related Art
It is well known that there is a demand for image displays that provide high quality images. The performance of image displays is typically improved with an increase in a number of pixels. Currently, a pixel count for a standard display is about 1280 pixels×about 1024 pixels, whereas a display having a high pixel count includes about 5,120 pixels×4,096 pixels.
Typically, a number of complex components provide for generation of images using image displays. For example, the electro-optical modulators (EOM) that enable electronic image sources—especially high pixel count modulators—are difficult to fabricate and costly. Exemplary EOM include liquid crystal display (LCD) panels and micro-electromechanical system (MEMS) components. Problems associated with these technologies include low yield due to “dead” pixels as well as manufacturing challenges associated with precise placement of spacers and maintaining various film and layer thicknesses. Some electro-optical image modulators have a surplus of frame rate compared to the rate required to present a high-quality image within the integration time of the human visual system.
One example of an EOM that has an excess frame rate includes the MEMS devices described in U.S. Pat. No. 4,662,746, “Spatial Light Modulator and Method.” This patent discloses an electrostatically deflectable beam spatial light modulator with the beam composed of two layers of aluminum alloy and the hinge connecting the beam to the remainder of the alloy formed in only one of the two layers; this provides a thick stiff beam and a thin compliant hinge. The alloy is on a spacer made of photoresist which in turn is on a semiconductor substrate. The substrate contains addressing circuitry. For convenience, this device is referred to as a “digital mirror device” (DMD).
Another example of an EOM that has an excess frame rate is disclosed in U.S. Pat. No. 5,808,797 “Method and Apparatus for Modulating a light Beam.” This patent discloses a modulator for modulating incident rays of light, the modulator having a plurality of equally spaced apart elements, each of which includes a light reflective planar surface. The elements are arranged parallel to each other with their light reflective surfaces parallel to each other. The modulator includes means for supporting elements in relation to one another and means for moving particular ones of the elements relative to others so that the moved elements transit between a first configuration wherein the modulator acts to reflect the incident rays of light as a plane mirror, and a second configuration wherein the modulator diffracts the light reflected therefrom. In operation, the light reflective surfaces of the elements remain parallel to each other in both the first and the second configurations. The perpendicular spacing between the reflective surfaces of respective elements is equal to m/4 times the wavelength of the incident rays of light, wherein m=an even whole number or zero when the elements are in the first configuration and m=an odd whole number when the elements are in the second configuration.
An example of a resolution enhancement system using controlled illumination of excess frame rate light modulators is described in U.S. Pat. No. “Stroboscopic Illumination for Video Displays.” This patent discloses a flat panel autostereoscopic display having full resolution equal to the number of pixels in the two-dimensional light valve array, which serves to generate images. The display is achieved by incorporating an illumination system which makes use of stroboscopic light sources or continuously lit light sources in combination with electro-optical shutter means. The lighting system when used in conjunction with a 2-D flat panel display, achieves image resolution exceeding several times the pixel resolution of the light valve array.
Further examples of increasing resolution using sub-frame translation are described in U.S. Pat. No. 6,963,319 and U.S. Patent Application No. 2005/0025388A1. U.S. Pat. No. 6,963,319, entitled “Image display system and method” discloses a method of displaying an image that includes receiving image data for the image; buffering the image data for the image, including creating a frame of the image; defining a first sub-frame and at least a second sub-frame for the frame of the image; and displaying the first sub-frame and the second sub-frame, including synchronizing shifting a displayed image of the second sub-frame with displaying the second sub-frame. Patent Application No. 2005/0025388A1, entitled “Generating and displaying spatially offset sub-frames” discloses a method of displaying an image with a display device includes receiving image data for the image. A first sub-frame and a second sub-frame are generated based on combinations of pixel values from the image data. The method includes alternating between displaying the first sub-frame in a first position and displaying the second sub-frame in a second position spatially offset from the first position.
Unfortunately, the techniques disclosed do not provide desired benefits. For example, these techniques do not result in a fieldwise increase of resolution. Moreover, the techniques introduce unwanted blurring of the input images. Accordingly, improvement to technologies for resolution enhancement systems is warranted.
What are needed are techniques that provide for enhanced resolution for projection displays. Preferably, the techniques make use of existing components and require few additions to existing projection display designs.